We report on the observation of coherent confined acoustic phonons in CdSe core nanorods. We show that photobleaching and photoabsorption dynamics of nanocrystals, obtained with femtosecond pump-probe transient spectroscopy with a resonant pumping energy, exhibit evidence of oscillatory modulation, due to the modulation of the bandgap, despite the weak excitation regime (< mu J). In particular we found that the modulation frequency corresponds to the coherent radial breathing modes of the rods, suggesting that only the transverse ( radial) mode of coherent phonons is observed. No evidence of modulation is observed in the corresponding rod sample overcoated with a thin shell of CdS/ZnS, suggesting that the shell produces a strongly damped mechanism.
Ultrafast carrier dynamics and confined acoustic phonons in CdSe nanorods
Creti A;Manna L;Lomascolo M
2008
Abstract
We report on the observation of coherent confined acoustic phonons in CdSe core nanorods. We show that photobleaching and photoabsorption dynamics of nanocrystals, obtained with femtosecond pump-probe transient spectroscopy with a resonant pumping energy, exhibit evidence of oscillatory modulation, due to the modulation of the bandgap, despite the weak excitation regime (< mu J). In particular we found that the modulation frequency corresponds to the coherent radial breathing modes of the rods, suggesting that only the transverse ( radial) mode of coherent phonons is observed. No evidence of modulation is observed in the corresponding rod sample overcoated with a thin shell of CdS/ZnS, suggesting that the shell produces a strongly damped mechanism.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
